Tube-group heat exchangers

ABSTRACT

A cylindrical enclosure is provided with a central tubular nucleus and in between these, a first fluid flows following at least two parallel overlapping pseudo-helical paths which entirely occupy the volume between the enclosure and the nucleus. The paths are guided by vertical radial partitions and horizontal baffles. The baffles are interconnected by the radial partitions in twos (helical double-flow baffling) or in threes (helical triple-flow baffling) and have segmented cut-outs staggered in succession relative to one another. Also provided in the space between the enclosure and the nucleus and working in combination with the flow paths is a series of parallel tubes in which a second fluid flows, said tubes passing through the baffles. This exchanger allows not only a higher thermal performance as a result of better guidance of the fluid and at the same time a higher out-put, but also a considerable mechanical improvement by reduction of the range of the tubes of the tube-groups.

United St3tS Patent 1 Trepaud 1 May 8,1973

I54] TUBE-GROUP HEAT EXCHANGERS [76] Inventor: Georges Trepaud, 1 Rond Point Bugeaud, Paris, France 22 Filed: Junel,l97l

21 Appl.N0.: 148,677

[52] US. Cl. ..l65/l6l [51] ..F28f 9/22 [58] Field of Search ..l65/160, I61

[56] References Cited FOREIGN PATENTS OR APPLICATIONS Primary Examiner-Meyer Perlin Assistant Examiner-William C. Anderson Attorney-Robert E. Burns and Emmanuel J. Lobato [57] ABSTRACT A cylindrical enclosure is provided with a central tubular nucleus and in between these, a first fluid flows following at least two parallel overlapping pseudo-helical paths which entirely occupy the volume between the enclosure and the nucleus. The paths are guided by vertical radial partitions and horizontal baffles. The baffles are interconnected by the radial partitions in twos (helical double-flow baffling) or in threes (helical triple-flow baffling) and have segmented cut-outs staggered in succession relative to one another. Also provided in the space between the enclosure and the nucleus and working in combination with the flow paths is a series of parallel tubes in which a second fluid flows, said tubes passing through the baffles. This exchanger allows not only a higher thermal performance as a result of better guidance of the fluid and at the same time a higher out-put, but also a considerable mechanical improvement by reduction of the range of the tubes of the tube-groups.

3 Claims, 5 Drawing Figures Patehted May-8, 1973 3 Sheets-Sheet l FiG.1

Patented 7 May 8, 1973 s Shets-Sheet FiG.3

FI'GA Patented May 8, 1973 3 Sheets-Sheet 5 FiG.5

TUBE-GROUP HEAT EXCHANGERS The present invention relates to tube-group heat exchangers of the type comprising a cylindrical enclosure and a central tubular nucleus between which a first fluid flows, following a pseudo-helical path, and a group of parallel tubes disposed in the space between said enclosure and the central nucleus, a second fluid flowing in said tubes. The invention aims more particularly at improving the performance of this type of apparatus, notably as regards guidance of the first fluid and the heat-exchange effected in the case of highvolume flow of fluid, or when the acceptable pressure drop on the circuit of the first fluid must be reduced, without however increasing the dimensions and thus the price of the apparatus.

French Pat. No. 797 552, concerning an Accelerated-circulation vertical evaporator for producing cold" made known a heat-exchanger of the type indicated above, in which a first refrigerating fluid circulates in the tubes of the tube-group, while a second fluid circulates around the tubes in the enclosure surrounding them following a pseudo-helical path, during which it loses a large proportion of its calories. In this patent, the circulation of the second fluid along a pseudo-helical path is obtained by baffles perpendicular to the group of tubes passing through them, having respectively segmental cut-outs staggered in succession one relative to the other, and interconnected by flat partition elements arranged in planes radial relative to the cylindrical envelope.

Compared to previous devices, this arrangement improves the transmission of heat between the fluids. However, when the flow of fluid guided in a pseudohelical course by the baffles is too high, or the univeral pressure drop must be small, it is appropriate to make large passage-openings for the fluid. For this purpose one may either space apart the tubes around which the second fluid passes in the enclosure, and through which the first, refrigerating fluid passes, but then the diameter of the apparatus (and its cost) must be increased, or the baffles may be spaced apart which tends to entail less efficient guidance of the second fluid, and to give the tubes too large a range, i.e., an excessive length between their points of fixture, on two successive baffles, so that the tubes will no longer be correctly supported.

Moreover, other heat-exchangers are known, made up of a cylindrical enclosure and a central tubular nucleus between which the two fluids circulate respectively in parallel overlapping helical courses. However, in these exchangers the heat-exchange between the fluids is no longer of the type effected in tube-group exchangers, in that it is effected across common helical ramps. This type of exchanger often entails certain drawbacks, particularly the fact that the helical ramps make it difficult to provide a good seal between the cylindrical enclosure and the ramp, which does not occur in the tube-group exchanger mentioned above.

In addition, yet another type of heat-exchanger is known, in which a first fluid circulates in a central tube, while a second fluid circulates between this tube and a cylindrical envelope of larger diameter, in parallel courses around said central tube, and between baffles in the form of partially truncated discs on diametrallyopposed parts. However, on the other hand, the parallel courses of the fluid are not helical, nor even pseudohelical, the said arrangement of truncated discs not allowing any considerable flow of fluid, and not ensuring good guidance of the fluid in the exchanger.

The object of the present invention is to increase the passage size for the fluid circulating around the tubes in the enclosure, without increasing the dimensions of the apparatus or the range of the tubes, while ensuring good guidance of this fluid, by a new arrangement of said baffles in the enclosure of the heat-exchanger.

This problem is solved according to the invention by the fact that the heat-exchanger comprises, in combination with said tube-group, at least two parallel overlapping pseudo-helical courses entirely occupying the volume between the enclosure and the central tube nucleus, and are made up, in a way known in itself, of plane baffles perpendicular to the tube-group passing through them, and having segmental cut-outs staggered in succession one relative to the other, said baffles being interconnected, at least in twos, by plane radial partitions forming a constant angle between themselves.

As indicated, these baffles are interconnected by radial partitions, at least in twos (in the case of helical double-flow baffling), or in threes (helical triple-flow baffling), so as to interconnect the baffles of the same flow. In addition, the heat-exchanger according to the invention comprises at one end an inlet chamber for the fluid,=intended to split the fluid up among the different flows.

Thanks to the device according to the invention, it is possible to obtain not only a higher thermal performance than in devices at present known, in consequence of better guidance of the fluid and at the same time a higher output, but also considerable mechanical improvement by reduction of the range of the tubes of the tube-group, with a considerable reduction in the pressure drop of such a device.

There will be described and illustrated with reference to the annexed drawing, and by way of example, an embodiment of the device according to the in vention.

In the drawing:

FIG. 1 is a perspective view, partly sectioned, of the cylindrical body of a heat-exchanger according to the invention;

FIG. 2 is a developed plan diagram of the baffling of the exchanger in FIG. 1;

FIG. 3 is a developed plan diagram of the baffling of the exchanger in FIG. 1 with an inlet and an outlet chamber for the fluid;

FIG. 4 is a perspective plan view of an inlet and distribution chamber for the fluid entering the exchanger according to the invention, comprising a double-flow baffling; and

FIG. 5 is a developed plan diagram of a three-flow baffle with an inlet chamber and an outlet chamber for the fluid.

Referring to the drawings, FIG. 1 shows the central part of a heat-exchanger, arranged vertically, comprising a cylindrical enclosure 1, defined at both ends by circular plates 3 and 4 through which passes a central tube 2. The space between plates 3 and 4 and between enclosure 1 and tube 2 contains on the one hand, a group of narrow-diameter tubes, shown diagrammatically, for clarity, by a number of small mixed vertical dashes parallel to the axis of the assembly 1-2 and equally distributed between enclosure 1 and central tube 2, in which the ubtes there circulate a fluid. The space, on the other hand, also contains an assembly of baffles, such as K1, K2, K3, K4, C1, C2, C3, between which a first fluid circulates, passing around the tubes, in which the other, or second fluid flows, both fluids exchanging heat through the walls of said tubes.

In the example shown in FIG. 1. a double-flow baffling has been obtained, i.e., the baffles are arranged and interconnected in such a way that they guide the fluid in two parallel courses inside the enclosure 1. In order better to illustrate this arrangement, reference will at the same time be made to FIG. 1 and to FIG. 2, which is a developed diagram of the device in FIG. 1.

In order to obtain two parallel courses of the fluid, the baffles of the apparatus are interconnected in twos successively (K1, K2, K3, K4) on the other hand, C1, C2, C3, on the other) by plane radial partitions (5, 6, 7

on the one hand, 8, 9, on the other). It is presumed that the fluid arrives at the exchanger in the direction of arrow e and enters through inlet E (shown as a circle in FIG. 1). It will be noted that the fluid inlet E is so placed that baffle K1 distributes the fluid equally between the entries to the two courses, which will now be studied in detail. The part of the fluid entering the exchanger through the lower half of the circular opening E, situated below baffle K1, is stopped on the left by plane radial partition 10, closing off all access to the left between cylinder 1, tube 2 and plate 3, and baffles K1 and C1. The fluid thus advances between these walls, turning around tube 2 anti-clockwise and, as it again meets the opposite face of plate 10, it is forced to rise between radial partition (connecting K1 to K2) and plate 10, as all the baffles have a segmental opening provided for this purpose, enabling them to be interconnected, leaving access passages for the fluid. Thus partition 8 connecting baffles Cl and C2 is staggered by, for example, 60 relative to partition 5, connecting baffles K1 and K2 and, in addition, the plane segmental openings of the baffles of one assembly and the vertical partitions which end at these points are also staggered relative to one another in order to make the fluid follow a pseudo-helical course. Thus the fluid rises between partitions 5 and 10, then advances between baffles C1 and K2, is forced to rise between partitions 6 and 9 and circulates between baffles C2 and K3, rises between partitions 7 and 9, then circulates between baffles C3 and K4, emerging through the lower semicircular opening of outlet 5 and escaping in the direction of arrow s. Outlet 5 is arranged relative to baffle K4 in a similar way to the arrangement of inlet E relative to baffle K].

The course, described above, adopted by the part of the fluid entering the exchanger at the lower part of inlet E is shown by an unbroken arrowed line in FIGS. 1 and 2. The course followed by the part of the fluid entering the exchanger at the upper part of the circular inlet E is similar to that described previously. The fluid, stopped at the left by partition 10, circulates anticlockwise between baffles K1 and C1, rises between partitons 5 and 8, circulates between baffles K2 and C2, rises between partitions 6 and 9, circulates between baffles K3 and C3, rises between partitions 7 and 11,

and finally circulates between K4 and plate 4, leaving through the upper part of outlet 5 in the direction of arrow s. The course, described above, adopted by the part of the fluid entering the exchanger by the upper part of opening E, is shown by a broken arrowed line in FIGS. 1 and 2.

- Thus it is seen in the example of FIGS. land 2 that both flows formed by the baffles and partitions inside enclosure 1 may be correctly and simply supplied without a special arrangement. A single cylindrical fluid feed tube may be connected to enclosure 1 at E, the first baffle distributing. the fluid equally between the two semi-circular openings formed. However, even in this case (double-flow) there may be provided, as is shown in FIG. 3, a feed-chamber 12 for fluid arriving in the direction of arrow s, and a collecting chamber 13 from which the fluid leaves in the direction of arrow s, E (and S) indicating the inlet (and the outlet) proper of the baffling whose walls l4, l5 and 16, without openings define two courses for the fluid.

FIG. 4 shows a special embodiment according to the invention of an inlet chamber 18 for the fluid entering the chamber in the direction of arrow e" through a tube 17. Chamber 18 is annular, and is contained between enclosures 1, tube 2, an end-plate p of cylindrical chamber 1 and a first baffle K; this chamber is divided into two compartments by means of a radial vertical partition 19 situated between tube 2 and enclosure 1 at the side opposite the fluid inlet 17. The fluid flows in the direction of arrows f, f into the chamber 17, towards two openings 20 and 21 in baffle K and situated one on either side of partition 19. The fluid, which is thus equally distributed to each side of central tube 2 in two courses, then enters both flows of the baffling in a downward movement in the direction of arrows i.

FIG. 5 is a developed plan diagram of a three-flow baffling for a heat-exchanger according to the invention, comprising an inlet chamber 22 which the fluid enters in the direction of arrow e and an outlet chamber 23 from which the fluid escapes in the direction of arrow s". The three flows are formed by the walls (without openings) 24, 25, 26, and 27, whose arrangement is similar to that in FIG. 1, the baffles in this, however, being united in threes by the radial partitions. In FIG. 5, L indicates the maximum range of the tubes and l the height of a floor (a floor occupying the volume of enclosure 1 contained between two consecutive baffles of the same fluid flow, e.g., the volume between baffles K1 and K2, C1 and C2, K2 and K3, C2 and C3, etc., in the case of double-flow baffling, or the volume between baffles K24 and K27 in the case of triple-flow baffling in FIG. 5). A distinction must be made here between the intermediate floors, such as (K1 K2), (K2 K3) or (C1 C2), in the case of double-flow baffling in FIGS. 1 and 2, and the terminal floors of the exchanger, e.g., (K1 K2) or (K3 K4). In fact, in the case of intermediate floors whose height is I, the value of the range of the tubes is l/n, if n is the number of flows in the baffling. This range is less than or equal to l (a single flow); but it is in any case less than the range of certain tubes of the terminal floors of the exchanger. In effect, it is seen from FIG. 1, for example, that certain tubes of the exchanger do not pass through the two first horizontal baffles K1 and CI, for the latter comprise segmental cut-outs. Thus, these tubes have a range equal to the height between plate 3 and baffle K2, which is greater than the range of the tubes passing directly through baffles K1 and Cl. In this case, the maximum range L of the tubes is therefore equal to;

where l is the height of a floor, i.e., the height between C3 and C2, between K1 and K2, between Cl and C2.

In the general case ofa baffling with n flows, one may state that the maximum range L of the tubes is:

where n l (single-flow) L 21 where n 2 (double-flow) L (3/2)l It may therefore be stated that, for a baffle system with n flows, and for the same given length of the cylindrical enclosure 1, the distance between successive baffles is reduced n times, for the same passage cross-section. The resultant advantage is that the fluid is better guided, which allows avoidance of dead zones, where the coefficient of thermal exchange is small and where deposits tend to form. In addition, without disturbing the external dimensions of the apparatus, it is possible to reduce the range of the tubes, which can only contribute to better maintenance of the said tubes.

Moreover, in the case where thermal calculation of the device leads to passage cross-sections for the fluid such as the spacing between baffles no longer ensures correct support of the tubes, it is possible, thanks to the arrangement of n flows in parallel for the fluid, to retain the maximum acceptable range L,,, choosing the number n of flows, such as:

while conserving the necessary passage cross-section without increasing the spacing of the tubes (which would increase the cost of the apparatus).

It will also be noted that the baffling according to the invention has another advantage in the case of verticular heat-exchangers in which there circulates a gas containing condensed products, and in which the condensates formed are collected at the level of each baffle, and flow along these baffles. In effect, the thickness of the flow film is the smaller in that the number of flows is raised and the thermal resistance of this film is thus reduced. Consequently, the universal heat-exchange coefficient is increased for the same pressure drop.

A particular application is that of dehydration of the gases compressed by refrigeration. The gas is treated by cooling, the water which it contains being then condensed and eliminated. In this case large volumes of fluid must be treated, and the pressure drops must remain small; the application of helical baffling with multiple flows is thus particularly advantageous here given that, on the one hand, one profits from an increase in the universal heat-exchange coefficient (as indicated above) and that, on the other hand, the condensed products are immediately separated by centrifugal force due to the pseudo-helical course of the guided fluid, and flow gravitationally along the baffling.

Iclaim:

1. In a heat exchanger of the tube-group type comprising a cylindrical enclosure and a central tubular nucleus between which a first fluid circulates with a high-volume flow In a pseudo-helical path, a group of parallel tubes arranged in the space between said enclosure and the central nucleus and in which there passes a second fluid, the improvement comprising in combination with the said tube-group, at least two pseudo-helical overlapping parallel courses occupying substantially completely the volume contained between the enclosure and the central tubular nucleus and constituted by plane baffles perpendicular to the tubegroup passing through them, and having segmental cutouts and being interconnected at least in pairs by radial plane partitions parallel to the longitudinal direction of the tubes, the segmental cut-outs of each pseudo-helical path being staggered successively the one with respect to the other, the said radial plane partitions which bind the edges of two such successive segmental cut-outs, forming a constant angle between them, and the apparatus comprising also an inlet opening providing a fluid partition between the said pseudo-helical pathes and means for introducing said first fluid in the inlet.

2. A heat exchanger as in claim 1, wherein the introducing means for the first fluid at one of its ends is constituted by an inlet tube opening into the enclosure of the exchanger by an opening in the lateral wall of said enclosure, said tube being cylindrical and arranged so that a diametric plane of said opening coincides with the plane of a baffle which separates the fluid supplied by the said tube into two equal parts distributing equally the first fluid between two flows.

3. A heat-exchanger as in claim 1, wherein the introducing means for the first fluid at one of its ends is constituted by an annular inlet chamber between the central tube and the cylindrical enclosure, which com prises a lateral inlet opening for the fluid, and an annular plate having two separate openings separated by a plane radial partition which divides the inlet chamber into two equal compartments opening into the inlets to the two overlapping parallel pseudo-helical flows distributing equally the first fluid between said two flows.

l t i I 

1. In a heat exchanger of the tube-group type comprising a cylindrical enclosure and a central tubular nucleus, between which a first fluid circulates with a high-volume flow in a pseudo-helical path, a group of parallel tubes arranged in the space between said enclosure and the central nucleus and in which there passes a second fluid, the improvement comprising in combination with the said tube-group, at least two pseudo-helical overlapping parallel courses occupying substantially completely the volume contained between the enclosure and the central tubular nucleus and constituted by plane baffles perpendicular to the tube-group passing through them, and having segmental cutouts and being interconnected at least in pairs by radial plane partitions parallel to the longitudinal direction of the tubes, the segmental cut-outs of each pseudo-helical path being staggered successively the one with respect to the other, the said radial plane partitions which bind the edges of two such successive segmental cut-outs, forming a constant angle between them, and the apparatus comprising also an inlet opening providing a fluid partition between the said pseudo-helical pathes and means for introducing said first fluid in the inlet.
 2. A heat exchanger as in claim 1, wherein the introducing means for the first fluid at one of its ends is constituted by an inlet tube opening into the enclosure of the exchanger by an opening in the lateral wall of said enclosure, said tube beinG cylindrical and arranged so that a diametric plane of said opening coincides with the plane of a baffle which separates the fluid supplied by the said tube into two equal parts distributing equally the first fluid between two flows.
 3. A heat-exchanger as in claim 1, wherein the introducing means for the first fluid at one of its ends is constituted by an annular inlet chamber between the central tube and the cylindrical enclosure, which comprises a lateral inlet opening for the fluid, and an annular plate having two separate openings separated by a plane radial partition which divides the inlet chamber into two equal compartments opening into the inlets to the two overlapping parallel pseudo-helical flows distributing equally the first fluid between said two flows. 